#include <iostream>
#include <array>    // C11 STL

int main() {
    using namespace std;
    array<double, 4> nums1 = {3.14, 5.0, 4.56, 9.9};
    array<double, 4> nums2;
    nums2 = nums1;  // valid for initialize array object

    nums2[-2] = 20.2;
    cout << "nums1[2]:" <<nums1[2] << " at " << &nums1[2] << endl;
    cout << "nums1[-2]:" <<nums2[-2] << " at " << &nums2[-2] << endl;
    cout << "nums1[2]:" <<nums2[2] << " at " << &nums2[2] << endl;
    return 0;
}